Then public transport costs wouldn’t go up, and would probably go down.

COMMUTERS could be hit with public transport fare increases of up to $150 a year when the carbon tax kicks in, confidential state government figures show.
[..]
the NSW Treasury estimated that the potential fare rises for all modes of public transport in NSW alone – due to increased electricity costs for trains and fuel costs for buses and ferries – could be expected at an average 3.4 per cent.
[..]
[NSW Premier Barry] O’Farrell said yesterday it was “crazy” that public transport would be hit by the tax when petrol for cars would be exempt: “This will create more pollution and defeat the whole purpose of a carbon tax.

“The federal government is crazy if it thinks this tax is going to reduce carbon emissions when it will lead to higher public transport fares and create an incentive for people to use their cars.”

Precisely Barry. We get told that car drivers are evil and public transport users are saints, and yet it’s those “saints” who pay a bigger share of the tax, which will be more likely to encourage them to drive than to stay on the trains and the buses and the ferries.

I keep saying it. This tax has less to do with climate change and more to do with social change, even economic change.